Array assays between surface bound binding agents or probes and target molecules in solution may be used to detect the presence of particular biopolymers. The surface-bound probes may be oligonucleotides, peptides, polypeptides, proteins, antibodies or other molecules capable of binding with target molecules in solution. Such binding interactions are the basis for many of the methods and devices used in a variety of different fields, e.g., genomics (in sequencing by hybridization, SNP detection, differential gene expression analysis, identification of novel genes, gene mapping, finger printing, etc.) and proteomics.
One typical array assay method involves biopolymeric probes immobilized in an array on a substrate such as a glass substrate or the like. A solution containing analytes that bind with the attached probes is placed in contact with the array substrate, covered with another substrate such as a coverslip or the like to form an assay area and placed in an environmentally controlled chamber such as an incubator or the like. Usually, the targets in the solution bind to the complementary probes on the substrate to form a binding complex. The pattern of binding by target molecules to biopolymer probe features or spots on the substrate produces a pattern on the surface of the substrate and provides desired information about the sample. In most instances, the target molecules are labeled with a detectable tag such as a fluorescent tag, chemiluminescent tag or radioactive tag. The resultant binding interaction or complexes of binding pairs are then detected and read or interrogated, for example by optical means, although other methods may also be used. For example, laser light may be used to excite fluorescent tags, generating a signal only in those spots on the biochip that have a target molecule and thus a fluorescent tag bound to a probe molecule. This pattern may then be digitally scanned for computer analysis.
As will be apparent, control of the assay environment and conditions contributes to increased reliability and reproducibility of the array assays. However, merely placing a substrate such as a coverslip over the array, as is commonly done, is often insufficient to allow precise control over the assay and permits leakage and evaporation of sample from the array site, where in many instances the quantity of sample is extremely limited.
During an array assay such as a hybridization assay, the assay is often performed at elevated temperatures and care must be taken so that the array does not dry out. Simply positioning a second slide over the array allows contents to leak or dry out during use, adversely impacting the assay. In addition, the substrate carrying the array cannot be tipped or moved from the horizontal position without risk that the substrate or cover slip will slip off. Maintaining the array in a humid environment may reduce drying-out, but offers only an incomplete solution.
Various closeable chambers or containers have been developed for conducting array-based assays which attempt to solve the problem of sample evaporation. However, many of these chambers fail to provide a complete seal around the array assay area. As such, leakage and evaporation of contents from the chamber still exists in these chambers. Furthermore, many of these chambers are complex and have numerous components that must be assembled by the user. Due to this complexity, the assembly process is often time-consuming and labor intensive.
Thus, there continues to be an interest in the development of new devices for array-based assays and methods of using the same. Of particular interest is the development of an array assay device, and methods of use thereof, that provides a fluid barrier around the assay area to prevent leakage and evaporation from the array assay area, is easy to assemble and use, includes a minimum of components, and that may also be capable of testing multiple samples with multiple arrays without cross-contamination.